1. Field of the Invention
The present invention pertains to methods and apparatus for filling bags or packages with dry particulate materials. More specifically, it pertains to automatic volumetric auger fill methods and apparatus for filling bags or packages with dry particulate materials.
2. Description of the Prior Art
One of the most modern types of processing machinery for filling bags, packages, pouches, etc. with dry particulate products is the machine referred to as the vertical form-fill-seal machine. With these machines, a flat continuous roll of film or paper may be formed into a tube, sealed at the bottom, filled and then sealed at the top.
There are these principal methods of proportioning dry products for filling bags being formed by vertical form-fill-seal (VFFS) machines. They are:
(1) Volumetric -- In this method, products drop from a supply hopper into cups of predetermined volumes. The cups are usually rotated on a plate to another point where the contents of the cup are dropped into the bag. This method is suitable for free-flowing granular products, such as rice, beans, popcorn and peanuts but not accurate for materials which do not flow readily or have a tendency to stick or bridge in the hopper and cups. PA1 (2) Net Weight Scales -- This method is used for products of high value. The product is weighed in a bucket prior to being dropped into a bag. It is not suited for use with fine powders, since a considerable portion of the product may stay suspended in the air when dropped from the bucket. PA1 (3) Auger Fill -- Auger filling is primarily used for powders, both free-flow and non-free flow. This is a volumetric method in which a given number of revolutions of an auger dispenses a desired volume of products.
The auger fill method is the only practical method of moving non-free flowing powders. However, this method has had a serious drawback in that it is a volumetric process. The accuracy of fill is dependent upon the consistency of the bulk density of the product being processed. Since the density of products may vary considerably, a strictly volumetric auger method may dispense more or less than required.
To overcome this drawback, methods of auger filling and net weight have been combined such as is used in Mateer Model 31-G2 filler manufactured by the Mateer-Burt Company of Wayne, Pa. In this prior art machine, the bag or other container is filled to 90 to 95 percent of the desired weight, strictly volumetricly at a high auger speed. At this point, the auger drive motor is reduced in speed and an electronic weighing system is energized, allowing the final portion to be dribble-filled to the desired weight cut-off point. However, this machine can be used only for pre-formed bags or rigid containers and each bag or container must be manually placed for filling. Thus, the machine is only semi-automatic and requires much more labor and time than the VFFS machines.